Lockdown key mechanism



J. l. CLARK Dec. 19, 1967 LOCKDOWN KEY MECHANISM Filed Sept. 12, 1966 F/E. I

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United States Patent 3,359,397 LOCKDOWN KEY MECHANISM John I. Clark, Stamford, Conn., assignor to Sperry Rand Corporation, New York, N.Y., a corporation of Delaware Filed Sept. 12, 1966, Ser. No. 578,663 8 Claims. (Cl. 200-169) ABSTRACT OF THE DISCLOSURE A mechanical latching device having first and second rest conditions effected by successive depressions of an input member, such as a typewriter key or the like. A lockdown mechanism is provided wherein a control element is alternately locked down and released in response to successive similar excursions of the input member. Bilevel signaling is readily obtained by coupling the control element to an output switching member having corresponding dual signaling positions.

The present invention relates to a control mechanism and more particularly to a lockdown device operative in response to the position of an element adapted to actuate a movable member.

It is well known to provide lockdown type control mechanisms for the keyboard portion of ofiice machines such as typewriters, calculators, or the like. For example, in many present day typewriters when it is desirous to employ upper case symbols and lettering, a particular key on the keyboard is depressed by the operator and simultaneously the key is locked down in the depressed position by a latching device actuated by the associated keystem. In the locked down position, related shifting mechanisms are actuated whereby subsequent depression of printing keys arranged on the keyboard will result in upper case printing during normal operation until the locked down key is released. The release function is carried out in many instances by depression of an independent key which actuates an appropriate mechanism to effectively release the latching device. It is also not uncommon to effect the release of such locked down key by toggling the holding portion of the latching device by means of a mechanism actuated by urging the associated keystem in a lateral direction with respect to the keytop.

In addition to the use of lockdown type mechanisms in ofiice machines, the general bilevel nature of such mechanisms leads to widespread adaptation throughout industry in many diverse applications where double action signaling is required. For example, in any control systems where binary type logic is employed a two level input device responsive to predetermined linear displacement, such as that of a keystem, may be advantageously utilized, i.e., the up position of the key may represent one binary character while the depressed position of the key may represent the other binary character.

In any mechanism of this nature, whether use is contemplated in a comparatively simple office machine or a complex oflice system, reliability is a highly desirable, if not indispensable requisite. In the case of a complete ofiice system where the overall operation is dependent upon selected input data entered by means of an array of mechanical keyboard mechanisms, failure or malfunction of that keyboard will have a crippling effect on the entire system and various associated operations. In the past, where speed of operation in addition to re liability has been a required characteristic, many problems have been encountered in attempts to provide a reliable lockdown mechanism without sacrificing speed in the operation thereof. These problems have been especially prevalent in those mechanisms where intermittent motion is imparted to a drive member disposed for interaction with adjacent parts moving relatively thereto.

It is an object of this invention to provide a novel control mechanism.

Another object is to provide a novel control mechanism wherein a control element is locked down after a first depression thereof and released by a second similar depression.

A further object is to provide a reliable mechanism wherein alternate positions of an output member are ob tained in response to successive similar operations of an input member.

Still a further object is to provide a novel control mechanism wherein a control element is alternately locked down and released in response to successive equal force depressions by the operator.

Yet another object is to provide a novel lockdown key mechanism which is alternately locked down and released in response to successive similardepressions of the key and wherein alternatively the release may be effected by an external mechanism notwithstanding key depression.

Still another object is to provide a highly reliable lockdown key mechanism which will not malfunction regardless of the force and rapidity of key depression.

The present invention contemplates a novel control mechanism for providing alternate positions of an output member in response to successive similar operations of an input member. In one embodiment the output membar is associated with the movable contact element of a circuit interrupter and the alternate positions of the output member provide successive open and closed conditions of the circuit interrupter. Thus, by successive depressions of the input member, the associated circuit is alternately disposed in an open and closed condition, i.e., no signal and signal conditions alternately prevail in response to a substantially identical input signal. It can be seen that the function of such a mechanism is readily adaptable in the input or other portions of present day control systems where bilevel signaling is quite common. The subject mechanism also lends itself for utilization in the keyboard of an ofiice machine, such as a calculator, where it is common to make keyboard entries which are applicable during several subsequent operations, e.g., a constant multiplier or divisor.

More specifically the mentioned embodiment contemplates an electrical switch having contacts associated with the position of a control element such as a keystem mounted for linear movement between a normal nondepressed position and a depressed control position. The normal position corresponding to open contact disposition and the depressed position accordingly corresponds to the closed condition. When the keystem is depressed to a predetermined longitudinal position a trip arm carried thereby engages a pivotally mounted bail member which under control of means coupling the bail and trip arm moves an integral latching lug to a position at which return of the keystem to its normal position is deterred. When the keystem is retained in its depressed control position, return to its normal position may be initiated by depression thereof which causes the coupling means between the bail and trip arm to operatively interact from a consideration of the detailed description which follows, in conjunction with the accompanying sheet of drawing wherein one principal embodiment of the invention is illustrated by way of example. It is to be expressly understood however, that the drawing is for illustrative purposes only and is not to be construed as defining the limits of the invention.

In the drawing wherein like reference characters refer to like parts throughout the several views:

FIG. 1 is a front view of a keyboard device which incorporates one embodiment of the novel control mechanism;

FIG. 2 is a fragmentary side e-levational view of the control mechanism shown in FIG. 1;

FIG. 3 is an exploded perspective view illustrating the parts of the novel control mechanism; and

FIGS. 4-9 schematically show the various inter-related operational disposition of the parts of the control mechanism when the input member is reciprocated between its two operative positions in response to an external activating force.

Now referring to the drawing for a detailed description of the present invention, and more particularly to FIG. 1, a keyboard switching mechanism is generally designated by the reference numeral and indicates by way of example apparatus incorporating an embodiment of the present invention. Mechanism 10 is adapted to operate the contacts of an electrical circuit interrupter or the like, generally designated by reference numeral 11, and represented for the purposes of this invention, as a two state switching device mounted by a bracket 12 and having an actuator member 13 that is biased normally in the position shown, corresponding to a first state. Actuator member 13, as in a conventional switch actuator, is illustrated as a button which responds to depression thereof to establish a second state when so depressed, e.g., the closed condition of contacts (not shown) of circuit interrupter 11. A keytop 14, preferably arranged in an array comprising a plurality of similar keytops, is attached to the end of a keystem which is reciprocally driven in response to depressions manually initiated at keytop 14 by an operator. When the keystem is in the position shown actuator member 13 is in its extended position and the contacts of circuit interrupter 11 remain open. As will be hereinafter described in further detail, a depression of keystem 15 results in the latching down of the keystem to hold actuator member 13 depressed and the contacts of circuit interrupter 11 are thereby held closed. By a successive depression of the keytop the keystem is delatched (or released) and consequently the circuit interrupter is returned to its normally open condition. Thus, it can be seen that the mechanism, now to be described in the embodiment shown, operatively provides for alternate states of circuit interrupter 11 in response to successive manual depression of keytop 14.

As mentioned above, a principal feature of the present invention is the means utilized for alternately latching and delatching keystem 15 in response to successive depressions of keytop 14 from which linear displacement of the keystem is derived. To this end, mechanism 10, shown in detail in FIGS. 1 and 2 and shown for convenience, schematically and in exploded relationship in FIG. 3, includes a mounting frame 16 on which keystem 15 and circuit interrupter 11 are mounted for operative engagement. Keystem 15 is slidable with respect to frame 16 and is guided at the top through a slot 17 (FIG. 1) in a peripheral flange portion 18 of frame 16 extending outwardly therefrom. The cross section of slot 17 corresponds substantially to the extending keytop mounting portion 20 of keystem 15. The excursions of the keystem are thereby physically limited to the distance between the lower surface 21 of keytop 14 and the upper surface of keystem protrusions 22 and 23 extending outwardly on opposite sides of keystem 15. A further limitation imposed .4 on the downward excursion of keystem 15 is evident from the description that follows.

The keystem is also guided by means of a slot 24 extending upwardly from the lower edge of keystem 15. The slot registers with a mounting rod 25 secured to frame 16. A collar 26, or the like, is secured to rod 25 to limit the axial freedom of keystem 15 along rod 25 and thereby effectively provide a slot through which keystem 15 is guided. Thus, keystem 15 is limited in downward and upward excursions by the length of slot 24 and protrusions 22 and 23, respectively.

A trip arm 27 is pivotally mounted to keystem 15 by a mounting stud 28. Rotation of arm 27 about stud 28 is limited by an extending finger 30 projecting outwardly from arm 27 and registering with a cutaway portion 31 of keystem 15. Thus, when trip arm 27 is caused to pivot, its travel is limited by the contact of finger 30 with the opposing side edges of cutaway portion 31. It should be noted that trip arm 27 is mounted on keystem 15 for independent pivotal action about stud 28 regardless of the relative position of keystem 15 with respect to frame 16.

Mounted pivotally on rod 25 is a bail member for performing the latching function, generally designated by reference numeral 32, the pivotal excursion of which is limited by an integral lug 33 extending outwardly therefrom and projecting through a hole 34 in mounting frame 16. It should be noted that bail 32 is generally U-shaped in configuration and is mounted on rod 25 by virtue of opposing mounting holes in the leg portions of such bail member, as illustrated in the exploded schematic View of FIG. 3. When bail 32 is caused to rotate in a counterclockwise direction the upper edge of hole 34 limits the travel of lug 33 and, likewise, when clockwise rotation takes place the excursion of bail 32 is limited by con tact between the bottom edge of hole 34 and lug 33. It can be further seen that bail 32, mounted as described above for rotation about rod 25 which is affixed to frame 16, includes two integral lug portions 35 and 36 extending inwardly therefrom for selective operative engagement with the lower edge 37 of trip arm 27 in a manner to be described hereinafter. FIGS. 2 and 3 show a ledge portion 38 of trip arm 27, which ledge portion serves to assure proper depth alignment and facilitates engagement between the lower edge 37 of arm 27 and integral lug portions 35 and 36.

Bail 32 further includes a latching lug 40, extending outwardly therefrom with respect to frame 16. At the limit of the clockwise excursion of bail 32, latching lug 40 is adapted to register with a notch 41 in keystem 15 when the keystem is in its lowermost position as determined by interaction between limiting slot 24 and mounting rod 25.

In the normal position of the subject control mechanism the elements are biased to the position shown in FIG. 1 by a toggle spring 42, which comprises several coil sections and diverging end arm portions 43 and 44. The spring is mounted between an axially disposed stud .5 on trip arm 27 and a stud 46 on upwardly extending mounting arm 47 on bail 32. By providing for slight coil compression when mounting the spring, an urging force may be exerted by spring end arm portions 43 and 44 on studs 45 and 46, respectively, which in turn bias trip arm 27 and hail 32 and accordingly provide moments about stud 28 and rod 25. Thus, in the normal condition of the mechanism 10 (shown in FIG. 1) trip arm 27 is urged in a counter-clockwise direction about stud 28 by means of the compressive force of spring 42 applied through end arm portion 43 and bail 32 is likewise urged in a counter-clockwise direction about rod 25 through spring end arm portion 44. The force exerted on trip arm 27 also urges keystem 15 upwardly to the position shown in FIG. 1. Freedom of movement provides for the biasing of keystem 15 with protrusions 22 and 23 resting against flange 18 as a result of force transmitted from spring 42 acting against bail 32 rotated to its most counter-clockwise position and arm 27 also in its most counter-clockwise position. In such normal condition actuator member 13 remains in its extended condition, i.e., circuit interrupter 11.is in its normally open position. To this end a leaf spring 48 is secured to a pin 50 extending from mounting bracket 12 and is resiliently urged against the lower edge of keystem 15. The disposition of spring 48 permits actuator member 13 to extend in its normally open condition when keystem 15 is in the normal position (FIG. 1). Alternatively, when the keystem 15 is translated downwardly a predetermined linear distance, actuator member 13 retracts under the force of spring 48 and circuit interrupter 11 goes to the closed position. By utilizing a leaf spring for this purpose, a desirable mechanical advantage is realized without exerting an unduly large force on member 13.

In addition to the force exerted on keystem 15 by toggle spring 42 and leaf spring 48 further means may be provided to accurately control the feel characteristics of the keytop 14 and keystem 15 combination as it relates to operation as an integral portion of a keyboard key array. In the embodiment shown, a torsion spring 51 is provided for such purpose. An integral L-shaped arm 52 extends from spring 51 and registers with slot 53 for urging keystem 15 upwardly. Various combinations of spring tension and slot contours enable preselection of any desired feel; however, the presense of spring 51 is not absolutely essential to restore keystem 15 to its normal position, in that toggle spring 42 can readily perform that function, as explained hereinabove.

(In accordance with the above described arrangement, operation for alternate actuation and deactuation of circuit interrupter 11 in response to successive depressions of keystem 15 is effected in the following manner. With reference to FIGS. 49, which schematically show various interrelated disposition of the elements described above during intermediate .states of latching and delatching of the keystem, the specific elements of the control mechanism shown in FIGS. 1 and 2 will be described during various operational steps. Initially, under normal rest conditions, the elements are'disposed in the relationship shown in FIG. 1. To facilitate the following operational description 21 hole 60 is shown in the keytop mounting portion 20 to illustrate the relationship between the slidably mounted keystem 15 and the fixed mounting frame 16. During rest conditions (FIG. 1) the hole is disposed midway between keytop 14 and flange portion 18.

In FIG. 4 the keystem 15 has been translated by an, operator to an intermediate position at which the lower edge 37 of trip arm 27 is contiguous with lug 36 on bail 32. By urging the keystem 15 to a predetermined longitudinal position to cause trip arm 27 to forcibly impinge on lug 36, bail 32 is caused to pivot to the position shown in FIG. 5. Toggle spring 42 shifts in a clockwise direction and latching lug 40 is positioned in notch 41. Simultaneously the shifted toggle spring pivots trip arm 27 in a clockwise direction to the position shown in FIG. 6 and keystem 15 is retained by interaction between latching lug 40 and a shoulder 61 formed by notch 41 such that hole 60 is aligned with flange 18. The keystem is thereby locked down and holds the circuit interrupter 11 (FIG. 1) in the closed or actuated position, i.e., the signal condition exists and keystem 15 is retained in the control position.

A subsequent depression of keystem 15 causes bail 27 to impinge on lug 35 of bail 32 as shown in FIG. 7. By further urging the keystem downwardly to the mentioned predetermined position (see hole 60 in FIG. 8) latching lug 40 is rotated out of notch 41 as bail 32 is snapped counter-clockwise due to the resulting opposite moment applied as a consequence of the position change of toggle spring 42 (FIG. 8). By then releasing the force applied to keytop 14, trip arm 27 is permitted to rotate counterclockwise to its original position and the keystem is urged upwardly (FIG. 9) until it reaches the position shown in FIG. 1. The circuit interrupter is thereby returned to its original condition associated with the normal rest position of the elements (FIG. 1).

In the event it is desirable to release the keystem without requiring a second depression of the keytop by the operator, it is now readily apparent that the mechanism lends itself to alternative delatching. Referring to the held down disposition of the elements as shown in FIG. 6 the bail 32 can be rotated counter-clockwise against the biasing force of spring 42 by external means (not shown) to the position shown in FIG. 8. This permits return of keystem 15 to its normal rest position without necessitating the impinging of trip arm 27 on lug .35 of bail 32.

Many advantages of the present invention have been explicitly and implicitly set forth throughout the above description, e.g., a simple, reliable control mechanism which obviates the need for an external release mechanism while still being conveniently adapted for release by external means when desired. The invention is also readily alterable to obtain any required characteristics within a broad range of depressive forces for alternately latching and delatching the novel mechanism.

Although a specific embodiment of the invention has been illustrated and describedin detail by way of example, it is to be understood that the invention is not limited thereto. Various changes may be made in the design and arrangement of parts without departing from the spirit and scope of the invention as defined by the appended claims, as will now be understood by those skilled in the art.

What is claimed is:

1. A lockdown key mechanism comprising,

(a) a longitudinally movable keystem,

(b) means for supporting said keystem,

(c) said support means fixed with respect to said key stem and including means for establishing a normal position of said keystem,

((1) means for biasing said keystem in said normal position, and a (e) latch means pivotally mounted on said support means for restraining said keystem at a control position remote from said normal position,

(f) said biasing means including means for operatively coupling said keystem and said latch means,

(g) said coupling means including trip means carried by said keystem for engagingly rotating said latch means to said restraining position when said keystem is moved to a predetermined longitudinal position from said normal position against said biasing means, whereby said keystem is retained in said control position.

2. A mechanism as set forth in claim 1 wherein said trip means comprise an arm pivotally mounted on said keystem and movable relative thereto to first and second predetermined positions, said arm being operable in said first position to engage said latch means when said keystem is moved from said normal position to said predetermined longitudinal position, and said arm being operable in said second position to engage said latch means for rotation thereof to release said keystem from said control position when said keystem is moved from said control position to said predetermined longitudinal position.

3. A mechanism as set forth in claim 2 wherein said latch means includes stop means for limiting rotation of said latch means to extended and retracted positions corresponding respectively to said normal and control positions of said keystem and said coupling means in addition to said trip means comprises a toggle spring connected between said arm and said latch means and is adapted to urge said arm in said first and second positions respectively when said latch means is disposed in said extended and retracted positions, said spring providing suflicient force to bias said keystem in said normal position under conditions where said latch means is disposed in said extended position.

4. A mechanism as set forth in claim 2 wherein said keystem includes an integral shoulder portion and said latch means comprise a bail member including a latching lug adapted to physically engage said shoulder portion to effect retention of said keystem under conditions where said latch means is rotated by said arm to said restraining position.

5. A mechanism as set forth in claim 3 wherein said toggle spring comprises a coil spring under compression, having diverging end portions extending tangentially outwardly from said coil, said spring end portions being secured to said arm and said latch means respectively whereby the disposition of said spring provides alternately a force and a counter force respectively to rotatively urge said latch means in said extended and retracted positions.

6. A mechanism as set forth in claim 5 wherein said keystem includes an integral shoulder portion, said latch means comprise a bail member including a latching lug extending in the path of said shoulder for effecting physial engagement therewith under conditions where said toggle spring rotates said latch to said retracted position.

7. In a lockdown key mechanism the combination comprising,

(a) switch means including contacts,

(b) a keystem,

(0) means for mounting said keystem for substantially reciprocal linear movement, said keystem being operable to a first position to open said contacts and a second position to close said switch contacts,

(d) means for normally biasing said keystem in said first position,

(e) a manually operable key member connected to said keystem to manually move said keystem from one position to the other to operate said switch contacts,

(f) a trip arm carried by said keystem for movement therewith, said trip arm being movable relative to said keystem to first and second predetermined positions, and

(g) bail means pivotally mounted on said mounting means and adapted for operable engagement with said trip arm, said bail means being selectively driven relative to said keystem by said trip arm to an extended position and to a retracted position,

(h) said biasing means operatively associated with said bail means for selectively urging said trip arm to said first and second predetermined positions for operable engagement with said bail means when said bail means is disposed respectively in said extended and retracted positions,

(i) said bail means including means :for restraining said keystem in said second position when said bail means is driven to said retracted position, whereby said contacts are retained closed when said keystem is translated to said second position in response to associated movement of said key member.

8. A mechanism as set forth in claim 7 wherein said keystem includes an integral shoulder portion, said means for restraining comprise an integral latching lug portion of said bail means, said trip arm is pivotally mounted on said keystem and said means operatively associated with said bail means includes a compressed toggle spring having diverging end portions extending outwardly therefrom, said toggle spring end portions being secured to said trip arm and said bail means respectively, whereby said toggle spring provides a rotative force to urge said bail means and dispose said lug portion in the longitudinal path of said shoulder portion of said keystem to effect retentive of said control element in said control position, and said toggle spring provides a counter-rotative force to release the bail means when said keystem is moved from said control position to said predetermined longitudinal position by said key member.

References Cited UNITED STATES PATENTS 3,312,808 4/1967 Dehn 200-169 ROBERT K. SCHAEFER, Primary Examiner;

H. O. JONES, Assistant Examiner. 

1. A LOCKDOWN KEY MECHANISM COMPRISING, (A) A LONGITUDINALLY MOVABLE KEYSTEM, (B) A LONGITUDINALLY MOVABLE SKEYSTEM, (C) SAID SUPPORT MEANS FIXED WITH RESPECT TO SAID KEYSTEM AND INCLUDING MEANS FOR ESTABLISHING A NORMAL POSITION OF SAID KEYSTEM, (D) MEANS FOR BIASING SAID KEYSTEM IN SAID NORMAL POSITION, AND (E) LATCH MEANS PIVOTALLY MOUNTED ON SAID SUPPORT MEANS FOR RESTRAINING SAID KEYSTEM AT A CONTROL POSITION REMOTE FROM SAID NORMAL POSITION, (F) SAID BIASING MEANS INCLUDING MEANS FOR OPERATIVELY COUPLING SAID KEYSTEM AND SAID LATCH MEANS, 